The past decade has seen quantum advances in the applications of technology to biomedical sciences. Among the more remarkable achievements has been the advent of whole genome sequencing allowing complete knowledge of the genomic DNA structure of innunierable organisms and the associated molecular biologic advances enabling comprehensive manipulation of these newly discovered genomic sequences. With this has come the ability to elevate scientific investigation of kidney disease and function to refined in vivo systems in the mammalian kidney. The validation of basic scientific discoveries in kidney disease now rests with studies in genetically engineered mouse models and naturally occurring human samples. The overarching objective of the Mouse Genetics and Cell Line Core in the Yale George M. O'Brien Kidney Center is to reduce barriers and facilitate application of in vivo mouse-based technologies to the study of kidney disease and to facilitate the extension of the studies to ex vivo cell-based systems derived from engineered mutant mice. The specific aims of the Core are to perform modification of genes of interest in bacterial artificial chromosome (BAC) for use in transgenic mice; to isolate of primary tubule ceNs and conditionally immortalized cell lines from specific nephron segments of mutant mouse strains; to facilitate generation of conditional knockout and knockin gene targeting strategies and constructs and to provide general resources for investigators in mouse genetic applications. This Core will Coordinate with the Renal Physiology and Phenotyping Core to assist investigators couple mouse genetic services with physiological studies. It will coordinate with the Human Genetics and Clinical Research to integrate new human disease gene discoveries with animal and cell line models. There is inherent synergy in the mouse model and cell line components of this Core as it allowing investigators access to the spectrum from defined in vivo models to ex vivo cell line models with identical genetic makeup. The Core now adds a novel mechanism for cell line generation based on technology developed by Core faculty, an improved BAC recombineering methodology and a new service in conditional knockout or knockin allele generation based the BAC technology.